Medical School, University of Ioannina, Dourouti, Division of Biomedical Research, Foundation for Research and Technology-Hellas, Institute of Molecular Biology and Biotechnology, Ioannina, 45110, Greece

Medical School, University of Ioannina, Dourouti, Division of Biomedical Research, Foundation for Research and Technology-Hellas, Institute of Molecular Biology and Biotechnology, Ioannina, 45110, Greece

Abstract

The oncoprotein SET/I2PP2A participates in various cellular mechanisms such as transcription, cell cycle regulation and cell migration. SET is also an inhibitor of the serine/threonine phosphatase PP2A, which is involved in the regulation of cell homeostasis. In zebrafish there are two paralogous
set
genes that encode Seta (269 aa) and Setb (275 aa) proteins which share 94% identity. We show here that
seta
and
set
b
are similarly expressed in the eye, the otic vesicle, the brain and the lateral line system, as indicated by
in situ
hybridization labeling. Whole mount immunofluorescence analysis revealed the expression of Seta/b proteins in the eye retina, the olfactory pit and the lateral line neuromasts. Loss-of-function studies using antisense morpholino oligonucleotides targeting both
seta
and
setb
genes (MOab), resulted in increased apoptosis, reduced cell proliferation and morphological defects. The morphant phenotypes were partially rescued when MOab morpholino was co-injected with human
SET
mRNA. Knock down of
setb
with a transcription-blocking morpholino (MOb) resulted in phenotypic defects comparable to those induced by
setb
gRNA/Cas9 injections.
In vivo
labelling of hair cells showed a significantly decreased number of neuromasts in MOab-, MOb- and gRNA/Cas9- injected embryos. Microarray analysis of MOab morphant transcriptome revealed differential expression in gene networks controlling transcription in the sensory organs, including the eye retina, the ear and the lateral line. Collectively, our results suggest that
seta
and
setb
are required during embryogenesis and play roles in the zebrafish sensory system development.